localtime.c

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/* Convert timestamp from pg_time_t to struct pg_tm.  */
 
/*
 * This file is in the public domain, so clarified as of
 * 1996-06-05 by Arthur David Olson.
 *
 * IDENTIFICATION
 *    src/timezone/localtime.c
 */
 
/*
 * Leap second handling from Bradley White.
 * POSIX.1-1988 style TZ environment variable handling from Guy Harris.
 */
 
/* this file needs to build in both frontend and backend contexts */
#include "c.h"
 
#include <fcntl.h>
 
#include "datatype/timestamp.h"
#include "pgtz.h"
 
#include "private.h"
#include "tzfile.h"
 
 
/*
 * Pacify gcc -Wcast-qual on char const * exprs.
 * Use this carefully, as the casts disable type checking.
 * This is a macro so that it can be used in static initializers.
 */
#define UNCONST(a) unconstify(char *, a)
 
#ifndef WILDABBR
/*
 * Someone might make incorrect use of a time zone abbreviation:
 *  1.  They might reference tzname[0] before calling tzset (explicitly
 *      or implicitly).
 *  2.  They might reference tzname[1] before calling tzset (explicitly
 *      or implicitly).
 *  3.  They might reference tzname[1] after setting to a time zone
 *      in which Daylight Saving Time is never observed.
 *  4.  They might reference tzname[0] after setting to a time zone
 *      in which Standard Time is never observed.
 *  5.  They might reference tm.TM_ZONE after calling offtime.
 * What's best to do in the above cases is open to debate;
 * for now, we just set things up so that in any of the five cases
 * WILDABBR is used. Another possibility: initialize tzname[0] to the
 * string "tzname[0] used before set", and similarly for the other cases.
 * And another: initialize tzname[0] to "ERA", with an explanation in the
 * manual page of what this "time zone abbreviation" means (doing this so
 * that tzname[0] has the "normal" length of three characters).
 */
#define WILDABBR "   "
#endif                          /* !defined WILDABBR */
 
static const char wildabbr[] = WILDABBR;
 
/*
 * The DST rules to use if TZ has no rules.
 * Default to US rules as of 2017-05-07.
 * POSIX does not specify the default DST rules;
 * for historical reasons, US rules are a common default.
 */
#ifndef TZDEFRULESTRING
#define TZDEFRULESTRING ",M3.2.0,M11.1.0"
#endif
 
/* TZNAME_MAXIMUM and types ttinfo, lsinfo, state have been moved to pgtz.h */
 
static int
leapcount(ATTRIBUTE_MAYBE_UNUSED struct state const *sp)
{
#if TZ_RUNTIME_LEAPS
    return sp->leapcnt;
#else
    return 0;
#endif
}
static void
set_leapcount(ATTRIBUTE_MAYBE_UNUSED struct state *sp,
              ATTRIBUTE_MAYBE_UNUSED int leapcnt)
{
#if TZ_RUNTIME_LEAPS
    sp->leapcnt = leapcnt;
#endif
}
static struct lsinfo
lsinfo(ATTRIBUTE_MAYBE_UNUSED struct state const *sp,
       ATTRIBUTE_MAYBE_UNUSED int i)
{
#if TZ_RUNTIME_LEAPS
    return sp->lsis[i];
#else
    unreachable();
#endif
}
static void
set_lsinfo(ATTRIBUTE_MAYBE_UNUSED struct state *sp,
           ATTRIBUTE_MAYBE_UNUSED int i,
           ATTRIBUTE_MAYBE_UNUSED struct lsinfo lsinfo)
{
#if TZ_RUNTIME_LEAPS
    sp->lsis[i] = lsinfo;
#endif
}
 
enum r_type
{
    JULIAN_DAY,                 /* Jn = Julian day */
    DAY_OF_YEAR,                /* n = day of year */
    MONTH_NTH_DAY_OF_WEEK       /* Mm.n.d = month, week, day of week */
};
 
struct rule
{
    enum r_type r_type;         /* type of rule */
    int         r_day;          /* day number of rule */
    int         r_week;         /* week number of rule */
    int         r_mon;          /* month number of rule */
    int_fast32_t r_time;        /* transition time of rule */
};
 
/*
 * Prototypes for static functions.
 */
 
static struct pg_tm *gmtsub(pg_time_t const *timep, int_fast32_t offset,
                            struct pg_tm *tmp);
static bool increment_overflow(int *ip, int j);
static bool increment_overflow_time(pg_time_t *tp, int_fast32_2s j);
static int_fast32_2s leapcorr(struct state const *sp, pg_time_t t);
static struct pg_tm *timesub(pg_time_t const *timep,
                             int_fast32_t offset, struct state const *sp,
                             struct pg_tm *tmp);
static bool tzparse(const char *name, struct state *sp, struct state const *basep);
 
 
/*
 * Section 4.12.3 of X3.159-1989 requires that
 *  Except for the strftime function, these functions [asctime,
 *  ctime, gmtime, localtime] return values in one of two static
 *  objects: a broken-down time structure and an array of char.
 * Thanks to Paul Eggert for noting this.
 */
 
static struct pg_tm tm;
 
/* Initialize *S to a value based on UTOFF, ISDST, and DESIGIDX.  */
static void
init_ttinfo(struct ttinfo *s, int_fast32_t utoff, bool isdst,
            desigidx_type desigidx)
{
    s->tt_utoff = utoff;
    s->tt_isdst = isdst;
    s->tt_desigidx = desigidx;
    s->tt_ttisstd = false;
    s->tt_ttisut = false;
}
 
static int_fast32_2s
detzcode(const char *const codep)
{
    int         i;
    int_fast32_2s
                maxval = TWO_31_MINUS_1,
                minval = -1 - maxval,
                result;
 
    result = codep[0] & 0x7f;
    for (i = 1; i < 4; ++i)
        result = (result << 8) | (codep[i] & 0xff);
 
    if (codep[0] & 0x80)
    {
        /*
         * Do two's-complement negation even on non-two's-complement machines.
         * This cannot overflow, as int_fast32_2s is wide enough.
         */
        result += minval;
    }
    return result;
}
 
static int_fast64_t
detzcode64(const char *const codep)
{
    int_fast64_t result;
    int         i;
    int_fast64_t one = 1;
    int_fast64_t halfmaxval = one << (64 - 2);
    int_fast64_t maxval = halfmaxval - 1 + halfmaxval;
    int_fast64_t minval = -TWOS_COMPLEMENT(int_fast64_t) - maxval;
 
    result = codep[0] & 0x7f;
    for (i = 1; i < 8; ++i)
        result = (result << 8) | (codep[i] & 0xff);
 
    if (codep[0] & 0x80)
    {
        /*
         * Do two's-complement negation even on non-two's-complement machines.
         * If the result would be minval - 1, return minval.
         */
        result -= !TWOS_COMPLEMENT(int_fast64_t) && result != 0;
        result += minval;
    }
    return result;
}
 
/* Input buffer for data read from a compiled tz file.  */
union input_buffer
{
    /* The first part of the buffer, interpreted as a header.  */
    struct tzhead tzhead;
 
    /*
     * The entire buffer.  Ideally this would have no size limits; the
     * following should suffice for practical use.
     */
    char        buf[2 * sizeof(struct tzhead) + 2 * sizeof(struct state)
                    + 4 * TZ_MAX_TIMES];
};
 
/* Local storage needed for 'tzloadbody'.  */
union local_storage
{
    /* The results of analyzing the file's contents after it is opened.  */
    struct file_analysis
    {
        /* The input buffer.  */
        union input_buffer u;
 
        /* A temporary state used for parsing a TZ string in the file.  */
        struct state st;
    }           u;
 
    /* PG: we don't need the "fullname" member */
};
 
/* These tzload flags can be ORed together, and fit into 'char'.  */
enum
{
TZLOAD_FROMENV = 1};            /* The TZ string came from the environment.  */
enum
{
TZLOAD_TZSTRING = 2};           /* Read any newline-surrounded TZ string.  */
enum
{
TZLOAD_TZDIR_SUB = 4};          /* TZ should be a file under TZDIR.  */
 
/*
 * Load tz data from the file named NAME into *SP.  Respect TZLOADFLAGS.
 * Use **LSPP for temporary storage.  Return 0 on
 * success, an errno value on failure.
 * PG: If "canonname" is not NULL, then on success the canonical spelling of
 * given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
 */
static int
tzloadbody(char const *name, char *canonname,
           struct state *sp, char tzloadflags,
           union local_storage **lspp)
{
    int         i;
    int         fid;
    int         stored;
    ssize_t     nread;
    union local_storage *lsp = *lspp;
    union input_buffer *up;
    int         tzheadsize = sizeof(struct tzhead);
 
    sp->goback = sp->goahead = false;
 
    if (!name)
    {
        name = TZDEFAULT;
        if (!name)
            return EINVAL;
    }
 
    if (name[0] == ':')
        ++name;
 
    /*
     * The IANA code goes to a great deal of trouble here to try to prevent
     * inappropriate file accesses.  That seems unnecessary for PG since we
     * won't run as root.  pg_open_tzfile() does go to some effort to prevent
     * accesses outside the designated zoneinfo tree, though.
     */
    fid = pg_open_tzfile(name, canonname);
    if (fid < 0)
        return ENOENT;          /* pg_open_tzfile may not set errno */
 
    up = &lsp->u.u;
    nread = read(fid, up->buf, sizeof up->buf);
    if (nread < tzheadsize)
    {
        int         err = nread < 0 ? errno : EINVAL;
 
        close(fid);
        return err;
    }
    if (close(fid) < 0)
        return errno;
 
    for (stored = 4; stored <= 8; stored *= 2)
    {
        char        version = up->tzhead.tzh_version[0];
        bool        skip_datablock = stored == 4 && version;
        int_fast32_t datablock_size;
        int_fast32_2s
                    ttisstdcnt = detzcode(up->tzhead.tzh_ttisstdcnt),
                    ttisutcnt = detzcode(up->tzhead.tzh_ttisutcnt),
                    leapcnt = detzcode(up->tzhead.tzh_leapcnt),
                    timecnt = detzcode(up->tzhead.tzh_timecnt),
                    typecnt = detzcode(up->tzhead.tzh_typecnt),
                    charcnt = detzcode(up->tzhead.tzh_charcnt);
        char const *p = up->buf + tzheadsize;
 
        /*
         * Although tzfile(5) currently requires typecnt to be nonzero,
         * support future formats that may allow zero typecnt in files that
         * have a TZ string and no transitions.
         */
        if (!(0 <= leapcnt
              && leapcnt <= (TZ_RUNTIME_LEAPS ? TZ_MAX_LEAPS : 0)
              && 0 <= typecnt && typecnt <= TZ_MAX_TYPES
              && 0 <= timecnt && timecnt <= TZ_MAX_TIMES
              && 0 <= charcnt && charcnt <= TZ_MAX_CHARS
              && 0 <= ttisstdcnt && ttisstdcnt <= TZ_MAX_TYPES
              && 0 <= ttisutcnt && ttisutcnt <= TZ_MAX_TYPES))
            return EINVAL;
        datablock_size
            = (timecnt * stored /* ats */
               + timecnt        /* types */
               + typecnt * 6    /* ttinfos */
               + charcnt        /* chars */
               + leapcnt * (stored + 4) /* lsinfos */
               + ttisstdcnt     /* ttisstds */
               + ttisutcnt);    /* ttisuts */
        if (nread < tzheadsize + datablock_size)
            return EINVAL;
        if (skip_datablock)
            p += datablock_size;
        else if (!((ttisstdcnt == typecnt || ttisstdcnt == 0)
                   && (ttisutcnt == typecnt || ttisutcnt == 0)))
            return EINVAL;
        else
        {
            int_fast64_t prevtr = -1;
            int_fast32_2s prevcorr = -1;
 
            set_leapcount(sp, leapcnt);
            sp->timecnt = timecnt;
            sp->typecnt = typecnt;
            sp->charcnt = charcnt;
 
            /*
             * Read transitions, discarding those out of pg_time_t range. But
             * pretend the last transition before TIME_T_MIN occurred at
             * TIME_T_MIN.
             */
            timecnt = 0;
            for (i = 0; i < sp->timecnt; ++i)
            {
                int_fast64_t at
                = stored == 4 ? detzcode(p) : detzcode64(p);
 
                sp->types[i] = at <= TIME_T_MAX;
                if (sp->types[i])
                {
                    pg_time_t   attime
                    = ((TYPE_SIGNED(pg_time_t) ? at < TIME_T_MIN : at < 0)
                       ? TIME_T_MIN : at);
 
                    if (timecnt && attime <= sp->ats[timecnt - 1])
                    {
                        if (attime < sp->ats[timecnt - 1])
                            return EINVAL;
                        sp->types[i - 1] = 0;
                        timecnt--;
                    }
                    sp->ats[timecnt++] = attime;
                }
                p += stored;
            }
 
            timecnt = 0;
            for (i = 0; i < sp->timecnt; ++i)
            {
                unsigned char typ = *p++;
 
                if (sp->typecnt <= typ)
                    return EINVAL;
                if (sp->types[i])
                    sp->types[timecnt++] = typ;
            }
            sp->timecnt = timecnt;
            for (i = 0; i < sp->typecnt; ++i)
            {
                struct ttinfo *ttisp;
                unsigned char isdst,
                            desigidx;
                int_fast32_2s utoff = detzcode(p);
 
                /*
                 * Reject a UT offset equal to -2**31, as it might cause
                 * trouble both in this file and in callers. Also, it violates
                 * RFC 9636 section 3.2.
                 */
                if (utoff < -TWO_31_MINUS_1)
                    return EINVAL;
 
                ttisp = &sp->ttis[i];
                ttisp->tt_utoff = utoff;
                p += 4;
                isdst = *p++;
                if (!(isdst < 2))
                    return EINVAL;
                ttisp->tt_isdst = isdst;
                desigidx = *p++;
                if (!(desigidx < sp->charcnt))
                    return EINVAL;
                ttisp->tt_desigidx = desigidx;
            }
            for (i = 0; i < sp->charcnt; ++i)
                sp->chars[i] = *p++;
 
            /*
             * Ensure '\0'-terminated, and make it safe to call ttunspecified
             * later.
             */
            memset(&sp->chars[i], 0, CHARS_EXTRA);
 
            /* Read leap seconds, discarding those out of pg_time_t range.  */
            leapcnt = 0;
            for (i = 0; i < leapcount(sp); i++)
            {
                int_fast64_t tr = stored == 4 ? detzcode(p) : detzcode64(p);
                int_fast32_2s corr = detzcode(p + stored);
 
                p += stored + 4;
 
                /*
                 * Leap seconds cannot occur before the Epoch, or out of
                 * order.
                 */
                if (tr <= prevtr)
                    return EINVAL;
 
                /*
                 * To avoid other botches in this code, each leap second's
                 * correction must differ from the previous one's by 1 second
                 * or less, except that the first correction can be any value;
                 * these requirements are more generous than RFC 9636, to
                 * allow future RFC extensions.
                 */
                if (!(i == 0
                      || (prevcorr < corr
                          ? corr == prevcorr + 1
                          : (corr == prevcorr
                             || corr == prevcorr - 1))))
                    return EINVAL;
                prevtr = tr;
                prevcorr = corr;
 
                if (tr <= TIME_T_MAX)
                {
                    struct lsinfo ls;
 
                    ls.ls_trans = tr;
                    ls.ls_corr = corr;
                    set_lsinfo(sp, leapcnt, ls);
                    leapcnt++;
                }
            }
            set_leapcount(sp, leapcnt);
 
            for (i = 0; i < sp->typecnt; ++i)
            {
                struct ttinfo *ttisp;
 
                ttisp = &sp->ttis[i];
                if (ttisstdcnt == 0)
                    ttisp->tt_ttisstd = false;
                else
                {
                    if (*p != true && *p != false)
                        return EINVAL;
                    ttisp->tt_ttisstd = *p++;
                }
            }
            for (i = 0; i < sp->typecnt; ++i)
            {
                struct ttinfo *ttisp;
 
                ttisp = &sp->ttis[i];
                if (ttisutcnt == 0)
                    ttisp->tt_ttisut = false;
                else
                {
                    if (*p != true && *p != false)
                        return EINVAL;
                    ttisp->tt_ttisut = *p++;
                }
            }
        }
 
        nread -= p - up->buf;
        memmove(up->buf, p, nread);
 
        /* If this is an old file, we're done.  */
        if (!version)
            break;
    }
    if ((tzloadflags & TZLOAD_TZSTRING) && nread > 2 &&
        up->buf[0] == '\n' && up->buf[nread - 1] == '\n' &&
        sp->typecnt + 2 <= TZ_MAX_TYPES)
    {
        struct state *ts = &lsp->u.st;
 
        up->buf[nread - 1] = '\0';
        if (tzparse(&up->buf[1], ts, sp))
        {
 
            /*
             * Attempt to reuse existing abbreviations. Without this,
             * America/Anchorage would consume 50 bytes for abbreviations, as
             * sp->charcnt equals 40 (for LMT AST AWT APT AHST AHDT YST AKDT
             * AKST) and ts->charcnt equals 10 (for AKST AKDT).  Reusing means
             * sp->charcnt can stay 40 in this example.
             */
            int         gotabbr = 0;
            int         charcnt = sp->charcnt;
 
            for (i = 0; i < ts->typecnt; i++)
            {
                char       *tsabbr = ts->chars + ts->ttis[i].tt_desigidx;
                int         j;
 
                for (j = 0; j < charcnt; j++)
                    if (strcmp(sp->chars + j, tsabbr) == 0)
                    {
                        ts->ttis[i].tt_desigidx = j;
                        gotabbr++;
                        break;
                    }
                if (!(j < charcnt))
                {
                    int         tsabbrlen = strnlen(tsabbr, TZ_MAX_CHARS - j);
 
                    if (j + tsabbrlen < TZ_MAX_CHARS)
                    {
                        char       *cp = sp->chars + j;
 
                        memcpy(cp, tsabbr, tsabbrlen);
                        cp += tsabbrlen;
                        *cp = '\0';
                        charcnt = j + tsabbrlen + 1;
                        ts->ttis[i].tt_desigidx = j;
                        gotabbr++;
                    }
                }
            }
            if (gotabbr == ts->typecnt)
            {
                sp->charcnt = charcnt;
 
                /*
                 * Ignore any trailing, no-op transitions generated by zic as
                 * they don't help here and can run afoul of bugs in zic 2016j
                 * or earlier.
                 */
                while (1 < sp->timecnt
                       && (sp->types[sp->timecnt - 1]
                           == sp->types[sp->timecnt - 2]))
                    sp->timecnt--;
 
                sp->goahead = ts->goahead;
 
                for (i = 0; i < ts->timecnt; i++)
                {
                    pg_time_t   t = ts->ats[i];
 
                    if (increment_overflow_time(&t, leapcorr(sp, t))
                        || (0 < sp->timecnt
                            && t <= sp->ats[sp->timecnt - 1]))
                        continue;
                    if (TZ_MAX_TIMES <= sp->timecnt)
                    {
                        sp->goahead = false;
                        break;
                    }
                    sp->ats[sp->timecnt] = t;
                    sp->types[sp->timecnt] = (sp->typecnt
                                              + ts->types[i]);
                    sp->timecnt++;
                }
                for (i = 0; i < ts->typecnt; i++)
                    sp->ttis[sp->typecnt++] = ts->ttis[i];
            }
        }
    }
    if (sp->typecnt == 0)
        return EINVAL;
 
    return 0;
}
 
/*
 * Load tz data from the file named NAME into *SP.  Respect TZLOADFLAGS.
 * Return 0 on success, an errno value on failure.
 * PG: If "canonname" is not NULL, then on success the canonical spelling of
 * given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
 */
static int
tzload(char const *name, char *canonname, struct state *sp, char tzloadflags)
{
    /* PG: our version of tzloadbody never reallocates *lspp */
    union local_storage *lsp;
    union local_storage ls;
 
    lsp = &ls;
    return tzloadbody(name, canonname, sp, tzloadflags, &lsp);
}
 
static const int mon_lengths[2][MONSPERYEAR] = {
    {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
    {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
};
 
static const int year_lengths[2] = {
    DAYSPERNYEAR, DAYSPERLYEAR
};
 
/* Is C an ASCII digit?  */
static bool
is_digit(char c)
{
    return '0' <= c && c <= '9';
}
 
/*
 * Given a pointer into a timezone string, scan until a character that is not
 * a valid character in a time zone abbreviation is found.
 * Return a pointer to that character.
 */
 
ATTRIBUTE_PURE_114833 static const char *
getzname(const char *strp)
{
    char        c;
 
    while ((c = *strp) != '\0' && !is_digit(c) && c != ',' && c != '-' &&
           c != '+')
        ++strp;
    return strp;
}
 
/*
 * Given a pointer into an extended timezone string, scan until the ending
 * delimiter of the time zone abbreviation is located.
 * Return a pointer to the delimiter.
 *
 * As with getzname above, the legal character set is actually quite
 * restricted, with other characters producing undefined results.
 * We don't do any checking here; checking is done later in common-case code.
 */
 
ATTRIBUTE_PURE_114833 static const char *
getqzname(const char *strp, const int delim)
{
    int         c;
 
    while ((c = *strp) != '\0' && c != delim)
        ++strp;
    return strp;
}
 
/*
 * Given a pointer into a timezone string, extract a number from that string.
 * Check that the number is within a specified range; if it is not, return
 * NULL.
 * Otherwise, return a pointer to the first character not part of the number.
 */
 
static const char *
getnum(const char *strp, int *const nump, const int min, const int max)
{
    char        c;
    int         num;
 
    if (strp == NULL || !is_digit(c = *strp))
        return NULL;
    num = 0;
    do
    {
        num = num * 10 + (c - '0');
        if (num > max)
            return NULL;        /* illegal value */
        c = *++strp;
    } while (is_digit(c));
    if (num < min)
        return NULL;            /* illegal value */
    *nump = num;
    return strp;
}
 
/*
 * Given a pointer into a timezone string, extract a number of seconds,
 * in hh[:mm[:ss]] form, from the string.
 * If any error occurs, return NULL.
 * Otherwise, return a pointer to the first character not part of the number
 * of seconds.
 */
 
static const char *
getsecs(const char *strp, int_fast32_t *const secsp)
{
    int         num;
    int_fast32_t secsperhour = SECSPERHOUR;
 
    /*
     * 'HOURSPERDAY * DAYSPERWEEK - 1' allows quasi-POSIX rules like
     * "M10.4.6/26", which does not conform to POSIX, but which specifies the
     * equivalent of "02:00 on the first Sunday on or after 23 Oct".
     */
    strp = getnum(strp, &num, 0, HOURSPERDAY * DAYSPERWEEK - 1);
    if (strp == NULL)
        return NULL;
    *secsp = num * secsperhour;
    if (*strp == ':')
    {
        ++strp;
        strp = getnum(strp, &num, 0, MINSPERHOUR - 1);
        if (strp == NULL)
            return NULL;
        *secsp += num * SECSPERMIN;
        if (*strp == ':')
        {
            ++strp;
            /* 'SECSPERMIN' allows for leap seconds.  */
            strp = getnum(strp, &num, 0, SECSPERMIN);
            if (strp == NULL)
                return NULL;
            *secsp += num;
        }
    }
    return strp;
}
 
/*
 * Given a pointer into a timezone string, extract an offset, in
 * [+-]hh[:mm[:ss]] form, from the string.
 * If any error occurs, return NULL.
 * Otherwise, return a pointer to the first character not part of the time.
 */
 
static const char *
getoffset(const char *strp, int_fast32_t *const offsetp)
{
    bool        neg = false;
 
    if (*strp == '-')
    {
        neg = true;
        ++strp;
    }
    else if (*strp == '+')
        ++strp;
    strp = getsecs(strp, offsetp);
    if (strp == NULL)
        return NULL;            /* illegal time */
    if (neg)
        *offsetp = -*offsetp;
    return strp;
}
 
/*
 * Given a pointer into a timezone string, extract a rule in the form
 * date[/time]. See POSIX Base Definitions section 8.3 variable TZ
 * for the format of "date" and "time".
 * If a valid rule is not found, return NULL.
 * Otherwise, return a pointer to the first character not part of the rule.
 */
 
static const char *
getrule(const char *strp, struct rule *const rulep)
{
    if (*strp == 'J')
    {
        /*
         * Julian day.
         */
        rulep->r_type = JULIAN_DAY;
        ++strp;
        strp = getnum(strp, &rulep->r_day, 1, DAYSPERNYEAR);
    }
    else if (*strp == 'M')
    {
        /*
         * Month, week, day.
         */
        rulep->r_type = MONTH_NTH_DAY_OF_WEEK;
        ++strp;
        strp = getnum(strp, &rulep->r_mon, 1, MONSPERYEAR);
        if (strp == NULL)
            return NULL;
        if (*strp++ != '.')
            return NULL;
        strp = getnum(strp, &rulep->r_week, 1, 5);
        if (strp == NULL)
            return NULL;
        if (*strp++ != '.')
            return NULL;
        strp = getnum(strp, &rulep->r_day, 0, DAYSPERWEEK - 1);
    }
    else if (is_digit(*strp))
    {
        /*
         * Day of year.
         */
        rulep->r_type = DAY_OF_YEAR;
        strp = getnum(strp, &rulep->r_day, 0, DAYSPERLYEAR - 1);
    }
    else
        return NULL;            /* invalid format */
    if (strp == NULL)
        return NULL;
    if (*strp == '/')
    {
        /*
         * Time specified.
         */
        ++strp;
        strp = getoffset(strp, &rulep->r_time);
    }
    else
        rulep->r_time = 2 * SECSPERHOUR;    /* default = 2:00:00 */
    return strp;
}
 
/*
 * Given a year, a rule, and the offset from UT at the time that rule takes
 * effect, calculate the year-relative time that rule takes effect.
 */
 
static int_fast32_t
transtime(const int year, const struct rule *const rulep,
          const int_fast32_t offset)
{
    bool        leapyear;
    int_fast32_t value;
    int         i;
    int         d,
                m1,
                yy0,
                yy1,
                yy2,
                dow;
 
    leapyear = isleap(year);
    switch (rulep->r_type)
    {
 
        case JULIAN_DAY:
 
            /*
             * Jn - Julian day, 1 == January 1, 60 == March 1 even in leap
             * years. In non-leap years, or if the day number is 59 or less,
             * just add SECSPERDAY times the day number-1 to the time of
             * January 1, midnight, to get the day.
             */
            value = (rulep->r_day - 1) * SECSPERDAY;
            if (leapyear && rulep->r_day >= 60)
                value += SECSPERDAY;
            break;
 
        case DAY_OF_YEAR:
 
            /*
             * n - day of year. Just add SECSPERDAY times the day number to
             * the time of January 1, midnight, to get the day.
             */
            value = rulep->r_day * SECSPERDAY;
            break;
 
        case MONTH_NTH_DAY_OF_WEEK:
 
            /*
             * Mm.n.d - nth "dth day" of month m.
             */
 
            /*
             * Use Zeller's Congruence to get day-of-week of first day of
             * month.
             */
            m1 = (rulep->r_mon + 9) % 12 + 1;
            yy0 = (rulep->r_mon <= 2) ? (year - 1) : year;
            yy1 = yy0 / 100;
            yy2 = yy0 % 100;
            dow = ((26 * m1 - 2) / 10 +
                   1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
            if (dow < 0)
                dow += DAYSPERWEEK;
 
            /*
             * "dow" is the day-of-week of the first day of the month. Get the
             * day-of-month (zero-origin) of the first "dow" day of the month.
             */
            d = rulep->r_day - dow;
            if (d < 0)
                d += DAYSPERWEEK;
            for (i = 1; i < rulep->r_week; ++i)
            {
                if (d + DAYSPERWEEK >=
                    mon_lengths[leapyear][rulep->r_mon - 1])
                    break;
                d += DAYSPERWEEK;
            }
 
            /*
             * "d" is the day-of-month (zero-origin) of the day we want.
             */
            value = d * SECSPERDAY;
            for (i = 0; i < rulep->r_mon - 1; ++i)
                value += mon_lengths[leapyear][i] * SECSPERDAY;
            break;
 
        default:
            unreachable();
    }
 
    /*
     * "value" is the year-relative time of 00:00:00 UT on the day in
     * question. To get the year-relative time of the specified local time on
     * that day, add the transition time and the current offset from UT.
     */
    return value + rulep->r_time + offset;
}
 
/*
 * Given a POSIX.1 proleptic TZ string, fill in the rule tables as
 * appropriate.
 */
 
static bool
tzparse(const char *name, struct state *sp, struct state const *basep)
{
    const char *stdname;
    const char *dstname = NULL;
    int_fast32_t stdoffset;
    int_fast32_t dstoffset;
    char       *cp;
    ptrdiff_t   stdlen,
                dstlen,
                charcnt;
    pg_time_t   atlo = TIME_T_MIN,
                leaplo = TIME_T_MIN;
 
    stdname = name;
    if (*name == '<')
    {
        name++;
        stdname = name;
        name = getqzname(name, '>');
        if (*name != '>')
            return false;
        stdlen = name - stdname;
        name++;
    }
    else
    {
        name = getzname(name);
        stdlen = name - stdname;
    }
    if (stdlen > TZNAME_MAXIMUM)    /* allow empty STD abbrev, unlike IANA */
        return false;
    name = getoffset(name, &stdoffset);
    if (name == NULL)
        return false;
    charcnt = stdlen + 1;
    if (basep)
    {
        if (0 < basep->timecnt)
            atlo = basep->ats[basep->timecnt - 1];
        set_leapcount(sp, leapcount(basep));
        if (0 < leapcount(sp))
        {
            int         i;
 
            for (i = 0; i < leapcount(sp); i++)
                set_lsinfo(sp, i, lsinfo(basep, i));
            leaplo = lsinfo(sp, leapcount(sp) - 1).ls_trans;
        }
    }
    else
        set_leapcount(sp, 0);   /* So, we're off a little.  */
    sp->goback = sp->goahead = false;
    if (*name != '\0')
    {
        struct rule start,
                    end;
        int         year,
                    yearbeg,
                    yearlim,
                    timecnt;
        pg_time_t   janfirst;
        int_fast32_t janoffset = 0;
 
        if (*name == '<')
        {
            dstname = ++name;
            name = getqzname(name, '>');
            if (*name != '>')
                return false;
            dstlen = name - dstname;
            name++;
        }
        else
        {
            dstname = name;
            name = getzname(name);
            dstlen = name - dstname;    /* length of DST abbr. */
        }
        if (!(0 < dstlen && dstlen <= TZNAME_MAXIMUM))
            return false;
        charcnt += dstlen + 1;
        if (*name != '\0' && *name != ',' && *name != ';')
        {
            name = getoffset(name, &dstoffset);
            if (name == NULL)
                return false;
        }
        else
            dstoffset = stdoffset - SECSPERHOUR;
 
        if (*name == '\0')
            name = TZDEFRULESTRING;
        if (!(*name == ',' || *name == ';'))
            return false;
 
        name = getrule(name + 1, &start);
        if (!name)
            return false;
        if (*name++ != ',')
            return false;
        name = getrule(name, &end);
        if (!name || *name)
            return false;
        sp->typecnt = 2;        /* standard time and DST */
 
        /*
         * Two transitions per year, from EPOCH_YEAR forward.
         */
        init_ttinfo(&sp->ttis[0], -stdoffset, false, 0);
        init_ttinfo(&sp->ttis[1], -dstoffset, true, stdlen + 1);
        timecnt = 0;
        janfirst = 0;
        yearbeg = EPOCH_YEAR;
 
        do
        {
            int_fast32_t yearsecs
            = year_lengths[isleap(yearbeg - 1)] * SECSPERDAY;
            pg_time_t   janfirst1 = janfirst;
 
            yearbeg--;
            if (increment_overflow_time(&janfirst1, -yearsecs))
            {
                janoffset = -yearsecs;
                break;
            }
            janfirst = janfirst1;
        } while (atlo < janfirst
                 && EPOCH_YEAR - YEARSPERREPEAT / 2 < yearbeg);
 
        while (true)
        {
            int_fast32_t yearsecs
            = year_lengths[isleap(yearbeg)] * SECSPERDAY;
            int         yearbeg1 = yearbeg;
            pg_time_t   janfirst1 = janfirst;
 
            if (increment_overflow_time(&janfirst1, yearsecs)
                || increment_overflow(&yearbeg1, 1)
                || atlo <= janfirst1)
                break;
            yearbeg = yearbeg1;
            janfirst = janfirst1;
        }
 
        yearlim = yearbeg;
        if (increment_overflow(&yearlim, years_of_observations))
            yearlim = INT_MAX;
        for (year = yearbeg; year < yearlim; year++)
        {
            int_fast32_t
                        starttime = transtime(year, &start, stdoffset),
                        endtime = transtime(year, &end, dstoffset),
                        yearsecs = year_lengths[isleap(year)] * SECSPERDAY;
            bool        reversed = endtime < starttime;
 
            if (reversed)
            {
                int_fast32_t swap = starttime;
 
                starttime = endtime;
                endtime = swap;
            }
            if (reversed
                || (starttime < endtime
                    && endtime - starttime < yearsecs))
            {
                if (TZ_MAX_TIMES - 2 < timecnt)
                    break;
                sp->ats[timecnt] = janfirst;
                if (!increment_overflow_time(&sp->ats[timecnt],
                                             janoffset + starttime)
                    && atlo <= sp->ats[timecnt])
                    sp->types[timecnt++] = !reversed;
                sp->ats[timecnt] = janfirst;
                if (!increment_overflow_time(&sp->ats[timecnt],
                                             janoffset + endtime)
                    && atlo <= sp->ats[timecnt])
                {
                    sp->types[timecnt++] = reversed;
                }
            }
            if (endtime < leaplo)
            {
                yearlim = year;
                if (increment_overflow(&yearlim, years_of_observations))
                    yearlim = INT_MAX;
            }
            if (increment_overflow_time(&janfirst, janoffset + yearsecs))
                break;
            janoffset = 0;
        }
        sp->timecnt = timecnt;
        if (!timecnt)
        {
            sp->ttis[0] = sp->ttis[1];
            sp->typecnt = 1;    /* Perpetual DST.  */
        }
        else if (years_of_observations <= year - yearbeg)
            sp->goback = sp->goahead = true;
    }
    else
    {
        dstlen = 0;
        sp->typecnt = 1;        /* only standard time */
        sp->timecnt = 0;
        init_ttinfo(&sp->ttis[0], -stdoffset, false, 0);
    }
    sp->charcnt = charcnt;
    cp = sp->chars;
    memcpy(cp, stdname, stdlen);
    cp += stdlen;
    *cp++ = '\0';
    if (dstlen != 0)
    {
        memcpy(cp, dstname, dstlen);
        cp += dstlen;
        *cp = '\0';
    }
    return true;
}
 
static void
gmtload(struct state *const sp)
{
    /* PG: for historical compatibility, use "GMT" not "UTC" as TZ abbrev */
    tzparse("GMT0", sp, NULL);
}
 
 
/*
 * The easy way to behave "as if no library function calls" localtime
 * is to not call it, so we drop its guts into "localsub", which can be
 * freely called. (And no, the PANS doesn't require the above behavior,
 * but it *is* desirable.)
 */
static struct pg_tm *
localsub(struct state const *sp, pg_time_t const *timep,
         struct pg_tm *const tmp)
{
    const struct ttinfo *ttisp;
    int         i;
    struct pg_tm *result;
    const pg_time_t t = *timep;
 
    if (sp == NULL)
        return gmtsub(timep, 0, tmp);
    if ((sp->goback && t < sp->ats[0]) ||
        (sp->goahead && t > sp->ats[sp->timecnt - 1]))
    {
        pg_time_t   newt;
        pg_time_t   seconds;
        pg_time_t   years;
 
        if (t < sp->ats[0])
            seconds = sp->ats[0] - t;
        else
            seconds = t - sp->ats[sp->timecnt - 1];
        --seconds;
 
        /*
         * Beware integer overflow, as SECONDS might be close to the maximum
         * pg_time_t.
         */
        years = seconds / SECSPERREPEAT * YEARSPERREPEAT;
        seconds = years * AVGSECSPERYEAR;
        years += YEARSPERREPEAT;
        if (t < sp->ats[0])
            newt = t + seconds + SECSPERREPEAT;
        else
            newt = t - seconds - SECSPERREPEAT;
 
        if (newt < sp->ats[0] ||
            newt > sp->ats[sp->timecnt - 1])
            return NULL;        /* "cannot happen" */
        result = localsub(sp, &newt, tmp);
        if (result)
        {
#if defined ckd_add && defined ckd_sub
            if (t < sp->ats[0]
                ? ckd_sub(&result->tm_year,
                          result->tm_year, years)
                : ckd_add(&result->tm_year,
                          result->tm_year, years))
                return NULL;
#else
            int_fast64_t newy;
 
            newy = result->tm_year;
            if (t < sp->ats[0])
                newy -= years;
            else
                newy += years;
            if (!(INT_MIN <= newy && newy <= INT_MAX))
                return NULL;
            result->tm_year = newy;
#endif
        }
        return result;
    }
    if (sp->timecnt == 0 || t < sp->ats[0])
    {
        i = 0;
    }
    else
    {
        int         lo = 1;
        int         hi = sp->timecnt;
 
        while (lo < hi)
        {
            int         mid = (lo + hi) >> 1;
 
            if (t < sp->ats[mid])
                hi = mid;
            else
                lo = mid + 1;
        }
        i = sp->types[lo - 1];
    }
    ttisp = &sp->ttis[i];
 
    /*
     * To get (wrong) behavior that's compatible with System V Release 2.0
     * you'd replace the statement below with t += ttisp->tt_utoff;
     * timesub(&t, 0, sp, tmp);
     */
    result = timesub(&t, ttisp->tt_utoff, sp, tmp);
    if (result)
    {
        result->tm_isdst = ttisp->tt_isdst;
#ifdef TM_ZONE
        result->TM_ZONE = UNCONST(&sp->chars[ttisp->tt_desigidx]);
#endif
    }
    return result;
}
 
 
struct pg_tm *
pg_localtime(const pg_time_t *timep, const pg_tz *tz)
{
    return localsub(&tz->state, timep, &tm);
}
 
 
/*
 * gmtsub is to gmtime as localsub is to localtime.
 *
 * PG: except we have a private "struct state" for GMT, so no sp is passed in.
 */
 
static struct pg_tm *
gmtsub(pg_time_t const *timep,
       int_fast32_t offset, struct pg_tm *tmp)
{
    struct pg_tm *result;
 
    /* GMT timezone state data is kept here */
    static struct state *gmtptr = NULL;
 
    if (gmtptr == NULL)
    {
        /* Allocate on first use */
        gmtptr = (struct state *) malloc(sizeof(struct state));
        if (gmtptr == NULL)
            return NULL;        /* errno should be set by malloc */
        gmtload(gmtptr);
    }
 
    result = timesub(timep, offset, gmtptr, tmp);
#ifdef TM_ZONE
 
    /*
     * Could get fancy here and deliver something such as "+xx" or "-xx" if
     * offset is non-zero, but this is no time for a treasure hunt.
     */
    tmp->TM_ZONE = UNCONST(offset ? wildabbr
                           : gmtptr->chars);
#endif                          /* defined TM_ZONE */
    return result;
}
 
struct pg_tm *
pg_gmtime(const pg_time_t *timep)
{
    return gmtsub(timep, 0, &tm);
}
 
/*
 * Return the number of leap years through the end of the given year
 * where, to make the math easy, the answer for year zero is defined as zero.
 */
 
static pg_time_t
leaps_thru_end_of_nonneg(pg_time_t y)
{
    return y / 4 - y / 100 + y / 400;
}
 
static pg_time_t
leaps_thru_end_of(pg_time_t y)
{
    return (y < 0
            ? -1 - leaps_thru_end_of_nonneg(-1 - y)
            : leaps_thru_end_of_nonneg(y));
}
 
static struct pg_tm *
timesub(const pg_time_t *timep, int_fast32_t offset,
        const struct state *sp, struct pg_tm *tmp)
{
    pg_time_t   tdays;
    const int  *ip;
    int_fast32_2s corr;
    int         i;
    int_fast32_t idays,
                rem,
                dayoff,
                dayrem;
    pg_time_t   y;
 
    /*
     * If less than SECSPERMIN, the number of seconds since the most recent
     * positive leap second; otherwise, do not add 1 to localtime tm_sec
     * because of leap seconds.
     */
    pg_time_t   secs_since_posleap = SECSPERMIN;
 
    corr = 0;
    i = sp ? leapcount(sp) : 0;
    while (--i >= 0)
    {
        struct lsinfo ls = lsinfo(sp, i);
 
        if (ls.ls_trans <= *timep)
        {
            corr = ls.ls_corr;
            if ((i == 0 ? 0 : lsinfo(sp, i - 1).ls_corr) < corr)
                secs_since_posleap = *timep - ls.ls_trans;
            break;
        }
    }
 
    /*
     * Calculate the year, avoiding integer overflow even if pg_time_t is
     * unsigned.
     */
    tdays = *timep / SECSPERDAY;
    rem = *timep % SECSPERDAY;
    rem += offset % SECSPERDAY - corr % SECSPERDAY + 3 * SECSPERDAY;
    dayoff = offset / SECSPERDAY - corr / SECSPERDAY + rem / SECSPERDAY - 3;
    rem %= SECSPERDAY;
 
    /*
     * y = (EPOCH_YEAR + floor((tdays + dayoff) / DAYSPERREPEAT) *
     * YEARSPERREPEAT), sans overflow.  But calculate against 1570 (EPOCH_YEAR
     * - YEARSPERREPEAT) instead of against 1970 so that things work for
     * localtime values before 1970 when pg_time_t is unsigned.
     */
    dayrem = tdays % DAYSPERREPEAT;
    dayrem += dayoff % DAYSPERREPEAT;
    y = (EPOCH_YEAR - YEARSPERREPEAT
         + ((1 + dayoff / DAYSPERREPEAT + dayrem / DAYSPERREPEAT
             - ((dayrem % DAYSPERREPEAT) < 0)
             + tdays / DAYSPERREPEAT)
            * YEARSPERREPEAT));
    /* idays = (tdays + dayoff) mod DAYSPERREPEAT, sans overflow.  */
    idays = tdays % DAYSPERREPEAT;
    idays += dayoff % DAYSPERREPEAT + 2 * DAYSPERREPEAT;
    idays %= DAYSPERREPEAT;
    /* Increase Y and decrease IDAYS until IDAYS is in range for Y.  */
    while (year_lengths[isleap(y)] <= idays)
    {
        int         tdelta = idays / DAYSPERLYEAR;
        int_fast32_t ydelta = tdelta + !tdelta;
        pg_time_t   newy = y + ydelta;
        int         leapdays;
 
        leapdays = leaps_thru_end_of(newy - 1) -
            leaps_thru_end_of(y - 1);
        idays -= ydelta * DAYSPERNYEAR;
        idays -= leapdays;
        y = newy;
    }
 
#ifdef ckd_add
    if (ckd_add(&tmp->tm_year, y, -TM_YEAR_BASE))
    {
        errno = EOVERFLOW;
        return NULL;
    }
#else
    if (!TYPE_SIGNED(pg_time_t) && y < TM_YEAR_BASE)
    {
        int         signed_y = y;
 
        tmp->tm_year = signed_y - TM_YEAR_BASE;
    }
    else if ((!TYPE_SIGNED(pg_time_t) || INT_MIN + TM_YEAR_BASE <= y)
             && y - TM_YEAR_BASE <= INT_MAX)
        tmp->tm_year = y - TM_YEAR_BASE;
    else
    {
        errno = EOVERFLOW;
        return NULL;
    }
#endif
    tmp->tm_yday = idays;
 
    /*
     * The "extra" mods below avoid overflow problems.
     */
    tmp->tm_wday = (TM_WDAY_BASE
                    + ((tmp->tm_year % DAYSPERWEEK)
                       * (DAYSPERNYEAR % DAYSPERWEEK))
                    + leaps_thru_end_of(y - 1)
                    - leaps_thru_end_of(TM_YEAR_BASE - 1)
                    + idays);
    tmp->tm_wday %= DAYSPERWEEK;
    if (tmp->tm_wday < 0)
        tmp->tm_wday += DAYSPERWEEK;
    tmp->tm_hour = rem / SECSPERHOUR;
    rem %= SECSPERHOUR;
    tmp->tm_min = rem / SECSPERMIN;
    tmp->tm_sec = rem % SECSPERMIN;
 
    /*
     * Use "... ??:??:60" at the end of the localtime minute containing the
     * second just before the positive leap second.
     */
    tmp->tm_sec += secs_since_posleap <= tmp->tm_sec;
 
    ip = mon_lengths[isleap(y)];
    for (tmp->tm_mon = 0; idays >= ip[tmp->tm_mon]; ++(tmp->tm_mon))
        idays -= ip[tmp->tm_mon];
    tmp->tm_mday = idays + 1;
    tmp->tm_isdst = 0;
#ifdef TM_GMTOFF
    tmp->TM_GMTOFF = offset;
#endif                          /* defined TM_GMTOFF */
    return tmp;
}
 
/*
 * Adapted from code provided by Robert Elz, who writes:
 *  The "best" way to do mktime I think is based on an idea of Bob
 *  Kridle's (so its said...) from a long time ago.
 *  It does a binary search of the pg_time_t space. Since pg_time_t's are
 *  just 32 bits, its a max of 32 iterations (even at 64 bits it
 *  would still be very reasonable).
 */
 
#ifndef WRONG
#define WRONG (-1)
#endif                          /* !defined WRONG */
 
/*
 * Normalize logic courtesy Paul Eggert.
 */
 
static bool
increment_overflow(int *ip, int j)
{
#ifdef ckd_add
    return ckd_add(ip, *ip, j);
#else
    int const   i = *ip;
 
    /*----------
     * If i >= 0 there can only be overflow if i + j > INT_MAX
     * or if j > INT_MAX - i; given i >= 0, INT_MAX - i cannot overflow.
     * If i < 0 there can only be overflow if i + j < INT_MIN
     * or if j < INT_MIN - i; given i < 0, INT_MIN - i cannot overflow.
     *----------
     */
    if ((i >= 0) ? (j > INT_MAX - i) : (j < INT_MIN - i))
        return true;
    *ip += j;
    return false;
#endif
}
 
static bool
increment_overflow_time(pg_time_t *tp, int_fast32_2s j)
{
#ifdef ckd_add
    return ckd_add(tp, *tp, j);
#else
    /*----------
     * This is like
     * 'if (! (TIME_T_MIN <= *tp + j && *tp + j <= TIME_T_MAX)) ...',
     * except that it does the right thing even if *tp + j would overflow.
     *----------
     */
    if (!(j < 0
          ? (TYPE_SIGNED(pg_time_t) ? TIME_T_MIN - j <= *tp : -1 - j < *tp)
          : *tp <= TIME_T_MAX - j))
        return true;
    *tp += j;
    return false;
#endif
}
 
static int_fast32_2s
leapcorr(struct state const *sp, pg_time_t t)
{
    int         i;
 
    i = leapcount(sp);
    while (--i >= 0)
    {
        struct lsinfo ls = lsinfo(sp, i);
 
        if (ls.ls_trans <= t)
            return ls.ls_corr;
    }
    return 0;
}
 
/*
 * Postgres-specific functions begin here.
 */
 
/*
 * Load the definition of the given time zone name into *sp.
 * Return true if successful, false if not.
 * If "canonname" is not NULL, then on success the canonical spelling of
 * given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
 *
 * "GMT" is always interpreted as the gmtload() definition, without attempting
 * to load a definition from the filesystem.  This has a number of benefits:
 * 1. It's guaranteed to succeed, so we don't have the failure mode wherein
 * the bootstrap default timezone setting doesn't work (as could happen if
 * the OS attempts to supply a leap-second-aware version of "GMT").
 * 2. Because we aren't accessing the filesystem, we can safely initialize
 * the "GMT" zone definition before my_exec_path is known.
 * 3. It's quick enough that we don't waste much time when the bootstrap
 * default timezone setting is later overridden from postgresql.conf.
 */
bool
pg_tzload(const char *name, char *canonname, struct state *sp)
{
    if (strcmp(name, "GMT") == 0)
    {
        gmtload(sp);
        /* Use given name as canonical */
        if (canonname)
            strcpy(canonname, name);
    }
    else if (tzload(name, canonname, sp, TZLOAD_TZSTRING) != 0)
    {
        if (name[0] == ':' || !tzparse(name, sp, NULL))
        {
            /* Unknown timezone. Fail our call instead of loading GMT! */
            return false;
        }
        /* For POSIX timezone specs, use given name as canonical */
        if (canonname)
            strcpy(canonname, name);
    }
    return true;
}
 
/*
 * Find the next DST transition time in the given zone after the given time
 *
 * *timep and *tz are input arguments, the other parameters are output values.
 *
 * When the function result is 1, *boundary is set to the pg_time_t
 * representation of the next DST transition time after *timep,
 * *before_gmtoff and *before_isdst are set to the GMT offset and isdst
 * state prevailing just before that boundary (in particular, the state
 * prevailing at *timep), and *after_gmtoff and *after_isdst are set to
 * the state prevailing just after that boundary.
 *
 * When the function result is 0, there is no known DST transition
 * after *timep, but *before_gmtoff and *before_isdst indicate the GMT
 * offset and isdst state prevailing at *timep.  (This would occur in
 * DST-less time zones, or if a zone has permanently ceased using DST.)
 *
 * A function result of -1 indicates failure (this case does not actually
 * occur in our current implementation).
 */
int
pg_next_dst_boundary(const pg_time_t *timep,
                     long int *before_gmtoff,
                     int *before_isdst,
                     pg_time_t *boundary,
                     long int *after_gmtoff,
                     int *after_isdst,
                     const pg_tz *tz)
{
    const struct state *sp;
    const struct ttinfo *ttisp;
    int         i;
    int         j;
    const pg_time_t t = *timep;
 
    sp = &tz->state;
    if (sp->timecnt == 0)
    {
        /* non-DST zone, use the defaulttype (now always 0) */
        ttisp = &sp->ttis[0];
        *before_gmtoff = ttisp->tt_utoff;
        *before_isdst = ttisp->tt_isdst;
        return 0;
    }
    if ((sp->goback && t < sp->ats[0]) ||
        (sp->goahead && t > sp->ats[sp->timecnt - 1]))
    {
        /* For values outside the transition table, extrapolate */
        pg_time_t   newt = t;
        pg_time_t   seconds;
        pg_time_t   tcycles;
        int64       icycles;
        int         result;
 
        if (t < sp->ats[0])
            seconds = sp->ats[0] - t;
        else
            seconds = t - sp->ats[sp->timecnt - 1];
        --seconds;
        tcycles = seconds / YEARSPERREPEAT / AVGSECSPERYEAR;
        ++tcycles;
        icycles = tcycles;
        if (tcycles - icycles >= 1 || icycles - tcycles >= 1)
            return -1;
        seconds = icycles;
        seconds *= YEARSPERREPEAT;
        seconds *= AVGSECSPERYEAR;
        if (t < sp->ats[0])
            newt += seconds;
        else
            newt -= seconds;
        if (newt < sp->ats[0] ||
            newt > sp->ats[sp->timecnt - 1])
            return -1;          /* "cannot happen" */
 
        result = pg_next_dst_boundary(&newt, before_gmtoff,
                                      before_isdst,
                                      boundary,
                                      after_gmtoff,
                                      after_isdst,
                                      tz);
        if (t < sp->ats[0])
            *boundary -= seconds;
        else
            *boundary += seconds;
        return result;
    }
 
    if (t >= sp->ats[sp->timecnt - 1])
    {
        /* No known transition > t, so use last known segment's type */
        i = sp->types[sp->timecnt - 1];
        ttisp = &sp->ttis[i];
        *before_gmtoff = ttisp->tt_utoff;
        *before_isdst = ttisp->tt_isdst;
        return 0;
    }
    if (t < sp->ats[0])
    {
        /* For "before", use the defaulttype (now always 0) */
        ttisp = &sp->ttis[0];
        *before_gmtoff = ttisp->tt_utoff;
        *before_isdst = ttisp->tt_isdst;
        *boundary = sp->ats[0];
        /* And for "after", use the first segment's type */
        i = sp->types[0];
        ttisp = &sp->ttis[i];
        *after_gmtoff = ttisp->tt_utoff;
        *after_isdst = ttisp->tt_isdst;
        return 1;
    }
    /* Else search to find the boundary following t */
    {
        int         lo = 1;
        int         hi = sp->timecnt - 1;
 
        while (lo < hi)
        {
            int         mid = (lo + hi) >> 1;
 
            if (t < sp->ats[mid])
                hi = mid;
            else
                lo = mid + 1;
        }
        i = lo;
    }
    j = sp->types[i - 1];
    ttisp = &sp->ttis[j];
    *before_gmtoff = ttisp->tt_utoff;
    *before_isdst = ttisp->tt_isdst;
    *boundary = sp->ats[i];
    j = sp->types[i];
    ttisp = &sp->ttis[j];
    *after_gmtoff = ttisp->tt_utoff;
    *after_isdst = ttisp->tt_isdst;
    return 1;
}
 
/*
 * Identify a timezone abbreviation's meaning in the given zone
 *
 * Determine the GMT offset and DST flag associated with the abbreviation.
 * This is generally used only when the abbreviation has actually changed
 * meaning over time; therefore, we also take a UTC cutoff time, and return
 * the meaning in use at or most recently before that time, or the meaning
 * in first use after that time if the abbrev was never used before that.
 *
 * On success, returns true and sets *gmtoff and *isdst.  If the abbreviation
 * was never used at all in this zone, returns false.
 *
 * Note: abbrev is matched case-sensitively; it should be all-upper-case.
 */
bool
pg_interpret_timezone_abbrev(const char *abbrev,
                             const pg_time_t *timep,
                             long int *gmtoff,
                             int *isdst,
                             const pg_tz *tz)
{
    const struct state *sp;
    const char *abbrs;
    const struct ttinfo *ttisp;
    int         abbrind;
    int         cutoff;
    int         i;
    const pg_time_t t = *timep;
 
    sp = &tz->state;
 
    /*
     * Locate the abbreviation in the zone's abbreviation list.  We assume
     * there are not duplicates in the list.
     */
    abbrs = sp->chars;
    abbrind = 0;
    while (abbrind < sp->charcnt)
    {
        if (strcmp(abbrev, abbrs + abbrind) == 0)
            break;
        while (abbrs[abbrind] != '\0')
            abbrind++;
        abbrind++;
    }
    if (abbrind >= sp->charcnt)
        return false;           /* not there! */
 
    /*
     * Unlike pg_next_dst_boundary, we needn't sweat about extrapolation
     * (goback/goahead zones).  Finding the newest or oldest meaning of the
     * abbreviation should get us what we want, since extrapolation would just
     * be repeating the newest or oldest meanings.
     *
     * Use binary search to locate the first transition > cutoff time.  (Note
     * that sp->timecnt could be zero, in which case this loop does nothing
     * and only the defaulttype entry will be checked.)
     */
    {
        int         lo = 0;
        int         hi = sp->timecnt;
 
        while (lo < hi)
        {
            int         mid = (lo + hi) >> 1;
 
            if (t < sp->ats[mid])
                hi = mid;
            else
                lo = mid + 1;
        }
        cutoff = lo;
    }
 
    /*
     * Scan backwards to find the latest interval using the given abbrev
     * before the cutoff time.
     */
    for (i = cutoff - 1; i >= 0; i--)
    {
        ttisp = &sp->ttis[sp->types[i]];
        if (ttisp->tt_desigidx == abbrind)
        {
            *gmtoff = ttisp->tt_utoff;
            *isdst = ttisp->tt_isdst;
            return true;
        }
    }
 
    /*
     * Not found yet; check the defaulttype, which is notionally the era
     * before any of the entries in sp->types[].
     */
    ttisp = &sp->ttis[0];
    if (ttisp->tt_desigidx == abbrind)
    {
        *gmtoff = ttisp->tt_utoff;
        *isdst = ttisp->tt_isdst;
        return true;
    }
 
    /*
     * Not there, so scan forwards to find the first one after the cutoff.
     */
    for (i = cutoff; i < sp->timecnt; i++)
    {
        ttisp = &sp->ttis[sp->types[i]];
        if (ttisp->tt_desigidx == abbrind)
        {
            *gmtoff = ttisp->tt_utoff;
            *isdst = ttisp->tt_isdst;
            return true;
        }
    }
 
    return false;               /* hm, not actually used in any interval? */
}
 
/*
 * Detect whether a timezone abbreviation is defined within the given zone.
 *
 * This is similar to pg_interpret_timezone_abbrev() but is not concerned
 * with a specific point in time.  We want to know if the abbreviation is
 * known at all, and if so whether it has one meaning or several.
 *
 * Returns true if the abbreviation is known, false if not.
 * If the abbreviation is known and has a single meaning (only one value
 * of gmtoff/isdst), sets *isfixed = true and sets *gmtoff and *isdst.
 * If there are multiple meanings, sets *isfixed = false.
 *
 * Note: abbrev is matched case-sensitively; it should be all-upper-case.
 */
bool
pg_timezone_abbrev_is_known(const char *abbrev,
                            bool *isfixed,
                            long int *gmtoff,
                            int *isdst,
                            const pg_tz *tz)
{
    bool        result = false;
    const struct state *sp = &tz->state;
    const char *abbrs;
    int         abbrind;
 
    /*
     * Locate the abbreviation in the zone's abbreviation list.  We assume
     * there are not duplicates in the list.
     */
    abbrs = sp->chars;
    abbrind = 0;
    while (abbrind < sp->charcnt)
    {
        if (strcmp(abbrev, abbrs + abbrind) == 0)
            break;
        while (abbrs[abbrind] != '\0')
            abbrind++;
        abbrind++;
    }
    if (abbrind >= sp->charcnt)
        return false;           /* definitely not there */
 
    /*
     * Scan the ttinfo array to find uses of the abbreviation.
     */
    for (int i = 0; i < sp->typecnt; i++)
    {
        const struct ttinfo *ttisp = &sp->ttis[i];
 
        if (ttisp->tt_desigidx == abbrind)
        {
            if (!result)
            {
                /* First usage */
                *isfixed = true;    /* for the moment */
                *gmtoff = ttisp->tt_utoff;
                *isdst = ttisp->tt_isdst;
                result = true;
            }
            else
            {
                /* Second or later usage, does it match? */
                if (*gmtoff != ttisp->tt_utoff ||
                    *isdst != ttisp->tt_isdst)
                {
                    *isfixed = false;
                    break;      /* no point in looking further */
                }
            }
        }
    }
 
    return result;
}
 
/*
 * Iteratively fetch all the abbreviations used in the given time zone.
 *
 * *indx is a state counter that the caller must initialize to zero
 * before the first call, and not touch between calls.
 *
 * Returns the next known abbreviation, or NULL if there are no more.
 *
 * Note: the caller typically applies pg_interpret_timezone_abbrev()
 * to each result.  While that nominally results in O(N^2) time spent
 * searching the sp->chars[] array, we don't expect any zone to have
 * enough abbreviations to make that meaningful.
 */
const char *
pg_get_next_timezone_abbrev(int *indx,
                            const pg_tz *tz)
{
    const char *result;
    const struct state *sp = &tz->state;
    const char *abbrs;
    int         abbrind;
 
    /* If we're still in range, the result is the current abbrev. */
    abbrs = sp->chars;
    abbrind = *indx;
    if (abbrind < 0 || abbrind >= sp->charcnt)
        return NULL;
    result = abbrs + abbrind;
 
    /* Advance *indx past this abbrev and its trailing null. */
    while (abbrs[abbrind] != '\0')
        abbrind++;
    abbrind++;
    *indx = abbrind;
 
    return result;
}
 
/*
 * If the given timezone uses only one GMT offset, store that offset
 * into *gmtoff and return true, else return false.
 */
bool
pg_get_timezone_offset(const pg_tz *tz, long int *gmtoff)
{
    /*
     * The zone could have more than one ttinfo, if it's historically used
     * more than one abbreviation.  We return true as long as they all have
     * the same gmtoff.
     */
    const struct state *sp;
    int         i;
 
    sp = &tz->state;
    for (i = 1; i < sp->typecnt; i++)
    {
        if (sp->ttis[i].tt_utoff != sp->ttis[0].tt_utoff)
            return false;
    }
    *gmtoff = sp->ttis[0].tt_utoff;
    return true;
}
 
/*
 * Return the name of the current timezone
 */
const char *
pg_get_timezone_name(pg_tz *tz)
{
    if (tz)
        return tz->TZname;
    return NULL;
}
 
/*
 * Check whether timezone is acceptable.
 *
 * What we are doing here is checking for leap-second-aware timekeeping.
 * We need to reject such TZ settings because they'll wreak havoc with our
 * date/time arithmetic.
 */
bool
pg_tz_acceptable(pg_tz *tz)
{
    struct pg_tm *tt;
    pg_time_t   time2000;
 
    /*
     * To detect leap-second timekeeping, run pg_localtime for what should be
     * GMT midnight, 2000-01-01.  Insist that the tm_sec value be zero; any
     * other result has to be due to leap seconds.
     */
    time2000 = (POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY;
    tt = pg_localtime(&time2000, tz);
    if (!tt || tt->tm_sec != 0)
        return false;
 
    return true;
}